Prosecutors in Ohio have said they may seek the death penalty in the case of the former school bus driver accused of the kidnap and rape of three women held prisoner at his home for years.

Ariel Castro, 52, made his first court appearance on Thursday when a judge set bond at $8m. The size of the bond means he is likely to remain in jail for some time. His court-appointed lawyer said he was unemployed and had little money.

At a news conference later, county prosecutor Timothy McGinty said that his office intends to pursue charges of kidnapping and sexual assault, as well as aggravated murder, which could carry the death penalty.

The aggravated murder charges would stem from the forced miscarriages that police say were suffered by one of the women at the hands of Castro, 52, who is accused of holding them captive at his house in west Cleveland. "The law of Ohio calls for the death penalty for those most depraved criminals who commit aggravated murder during the course of a kidnapping," McGinty said.

The city of Cleveland has already filed kidnapping and rape charges against Castro, who appeared briefly in a municipal court on Thursday. Castro was silent during the hearing, looking at the ground, biting his collar and signing documents with his handcuffed hands.

Brian Murphy, the assistant prosecuting attorney at Cuyahoga County, told Judge Lauren Moore that Castro's home "was a prison to these three women and the child". He added: "Today the situation is turned on him. Mr Castro stands before you a captive, in captivity, a prisoner."

Castro face threes counts of rape, relating to the women, and four counts of kidnap, which include the child. He did not enter a plea. The Guardian does not usually identify the victims of sexual assault but the names of the three women were circulated widely by family and law enforcement agencies for years during their disappearance.

Kathleen DeMetz, a public defender appointed by the court to represent Castro, said after the hearing that he would need to raise $800,000 cash to get out of jail. "The man doesn't have any money," she said. "He clearly doesn't have that."

DeMetz told the court that Castro was unemployed after being fired from his job driving school buses last November. She said he was on suicide watch in jail and was expected to be held in isolation. Police say Castro has waived his right to remain silent and has been talking extensively.

His two brothers, Pedro, 54, and Onil, 50, also appeared in court on Thursday to answer outstanding warrants for separate misdemeanor cases, and were released. Prosecutors said on Wednesday that there was no evidence that either of them were involved in the crimes allegedly committed by their brother.

Investigators say Castro lured the three victims into his car at the ages of 14, 16 and 20. When they were imprisoned at his home, the women were apparently bound by ropes and chains at times and were kept in different rooms, police say. Authorities said the women, who disappeared separately between 2002 and 2004, remembered leaving the confines of 2207 Seymour Avenue in west Cleveland only twice during their years in captivity. On both occasions they recalled being taken to a garage on the property, disguised in wigs and hats.

Authorities say the women had multiple forced miscarriages. McGinty said aggravated murder charges could be filed related to pregnancies terminated by force. McGinty said that Castro would be charged for every single act of sexual violence, assault and other crimes, suggesting the charges could number in the hundreds.

Grisly details of the women's ordeal have begun to emerge. Berry's baby was born in a plastic inflatable children's swimming pool on Christmas Day, 2006, authorities said. A paternity test will be conducted to determine the identity of her father. Castro has consented to a DNA test, officials said.

A police report obtained by the Plain Dealer said Castro forced another of his alleged captives, Michelle Knight, to deliver the baby and threatened to kill her if the infant did not survive. The baby stopped breathing, and Knight resuscitated the child by breathing into her, the report said.

The women and Castro have given lengthy statements to police, deputy police chief Ed Tomba said. None of the women gave any indication that Castro's two brothers, who had been in custody since Monday, were involved, Tomba said.

Police say the ordeal of Amanda Berry, 27, Gina DeJesus, 23, and Michelle Knight, 32, ended on Monday when Berry seized a chance to break free when Castro was out of the house. Berry hammered on the front door, attracting the attention of passers-by who helped her escape. She emerged with a six-year-old daughter, and made a now-famous 911 call in which she alerted the authorities.

Deborah Knight, grandmother of Michelle Knight, is hugged by a neighbour outside her home in Cleveland. Photograph: John Gress/Reuters

In newly released police audio tapes dating from Monday, an emergency dispatcher tells officer that she has just spoken to a woman who "says her name is Amanda Berry and that she had been kidnapped 10 years ago".

An officer on the recorded call says: "This might be for real." After police arrive at the house, women can be heard crying. An officer tells the dispatcher: "We found 'em. We found 'em."

Berry and DeJesus went home to relatives on Wednesday, while Knight remained in hospital at Metro Health Medical Center, where her condition was described as good. For reasons that remain unclear, the hospital had said a day earlier that all three victims had been released.

The Associated Press reported that Castro was accused of twice breaking the nose of his children's mother, knocking out a tooth, dislocating each shoulder and threatening to kill her and her daughters.

According to a 2005 domestic-violence filing in Cuyahoga County domestic relations court, Grimilda Figueroa alleged that Castro frequently abducted her daughters and kept them from her. Figueroa died in April 2012 after a battle with cancer.

Figueroa's father, Ismail Figueroa, said Wednesday that Castro would regularly lock his daughter inside a second-floor apartment in the house where they lived when they were first together. Grimilda was "not allowed to go nowhere," said Angel Villanueva, who is married to Grimilda's sister. No matter where she wanted to go, "it had to be with him."